A PON is one system for providing network access over the last mile, which is the final portion of a telecommunications network that delivers communication to customers. A PON is a P2MP network comprising an OLT at a CO, ONUs at user premises, and an ODN coupling the OLT to the ONUs. PONs may also comprise RNs located between the OLTs and the ONUs, for instance at the end of roads where multiple customers reside.
NG-PONs may combine TDM and WDM to support higher capacities so that increased numbers of users can be served by a single OLT with sufficient bandwidth per user. In such a TWDM PON, a WDM PON is overlaid on top of a TDM PON. In other words, different wavelengths are multiplexed together to share a single feeder fiber, and each wavelength is shared by multiple users using TDM.